In a systematic review and meta-analysis of 19 trials, people who underwent metabolic surgery saw 66% reduced odds for all-cause mortality (OR 0.34, 95% CI 0.25-0.46, P<0.00001) when compared with medical therapy, found Adrian Billeter, MD, PhD, of the University of Heidelberg in Germany, and colleagues.

Macrovascular complications of type 2 diabetes were also significantly reduced in people who underwent metabolic surgery compared with medical therapy (OR 0.38, 95% CI 0.22-0.67, P=0.0008), according to the study reported at Obesity Week, a joint meeting of the Obesity Society and the American Society for Metabolic and Bariatric Surgery (ASMBS).

"What we know so far from several well-done randomized controlled trials is that metabolic surgery is clearly superior in achieving glycemic control compared to medical therapy," Billeter said during his oral presentation of the findings. "However, what we don't know is if metabolic surgery also has an effect on the heart endpoints, such as mortality or cardiovascular events." Previous trials have been underpowered to determine this, he noted.

For the analysis, he and his colleagues identified six randomized controlled trials, 10 retrospective cohort studies, two prospective cohort studies, and one prospective case-control study. All analyses included, with an average follow-up of 7 years, were required to have a group of participants with type 2 diabetes who underwent metabolic surgery compared with a control group who received "conservative" treatment.

The total number of participants who underwent metabolic surgery included in the meta-analysis was over 13,000, and this group was compared with data for 88,000 individuals who received medical therapy only.

Across all the data included in the analysis, every trial and study favored metabolic surgery compared with medical therapy in regards to overall mortality. This reduced odds for mortality was even more pronounced when the analysis was restricted to just the three randomized controlled trials that measured this outcome (OR 0.18, 95% CI 0.03-1.17), the researchers reported.

Similar outcomes were found for cardiovascular mortality, which significantly favored metabolic surgery over medical therapy (OR 0.22, 95% CI 0.11-0.44, P<0.0001). "This is probably the most relevant outcome because this is what patients with type 2 diabetes die from," noted Billeter. These findings also held consistent when isolated to just the chances of myocardial infarction, which dropped after metabolic surgery (OR 0.35, 95% CI 0.19-0.63, P=0.0005).

"This study adds to the enormous amount of data demonstrating the profound and definitive effect of metabolic surgery on obesity, diabetes, and its complications that no other therapy can achieve, yet surgery remains vastly underutilized as a treatment," commented ASMBS president Samer Mattar, MD, in a statement. "While metabolic surgery is certainly not for everyone -- there are many factors to consider -- many are missing out on a transformational procedure."

At the session where the study was presented, the moderator, Cori McBride, MD, of the University of Nebraska Medical Center in Omaha, asked Billeter what the next steps are. "We know that metabolic surgery is better for glycemic control," Billeter replied. "All studies now with drugs -- especially liraglutide and empagliflozin -- focus on cardiovascular mortality. This is what we needed to show, that metabolic surgery is actually superior to those drugs."

"First of all it's cheaper in the long run, but it's probably also more effective," he continued. "This is the most important step to establish that metabolic surgery is the key treatment for type 2 diabetes."

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